Valve with pressure differential seating

ABSTRACT

A valve for use in oil and gas production or similar applications includes a plug or other flow barrier disposed in a cavity of a hollow valve body with a metal-to-metal sealing surface that is not reliant on any rubberized or elastomeric material to effect a seal. The figures and art described herein show that this novel feature can increase the ability of the valve to seal in high-pressure environments, and also increase the reliability of the valve when in cycling use.

FIELD OF THE INVENTION

The invention relates to an improved design for a valve that usesasymmetric pressure applied to a bushing and sealing mechanism to allowfor improved sealing performance and reduced maintenance requirements.Although the valve is primarily described in reference to a plug valve,it could be equally applicable to other types of valves, including butnot limited to a ball valve or gate valve.

BACKGROUND OF THE INVENTION

Valves generally comprise a valve body with an interior bore for thepassage of fluid, and a means of sealing off the interior bore to stopthe flow of fluid. Certain types of valves, such as plug valves or ballvalves, include a plug or ball that is capable of rotating between anopen position, in which fluid is allowed to flow through the interiorbore, and a closed position, in which the plug or ball blocks the flowof fluid through the interior bore. Other types of valves, such as gatevalves, include a gate that is vertically lowered to block the flow offluid through the interior bore. All of these types of valves are oftenused in connection with the production of hydrocarbons such as crude oilor natural gas.

The valve of the present invention will be primarily described in thecontext of an embodiment using a plug valve, but it could also be usedin ball valves, gate valves, or other types of valves. In someapplications, it might be preferable to use a ball valve, rather than aplug valve, which allows for more even distribution of the contactpressure around the seat. In any event, the particular type of valve isnot critical to the operation of the invention and the claims of thepresent application should not be interpreted as limited to any specifictype of flow barrier used in the valve. It will be readily apparent toone of ordinary skill in the art how to implement the present inventionin a type of valve other than a plug valve.

Plug valves require a sealing interface so that, when in the closedposition, the plug will contain the pressure of the fluid within theinterior bore of the valve. In many applications, such as the productionof hydrocarbons, interior pressures can be extremely high, on the orderof 15,000 pounds per square inch or higher. In addition, the fluidwithin the interior bore may be corrosive or otherwise potentiallydamaging to the seals. Accordingly, the integrity and reliability of thesealing interface is of utmost importance in the design of a plug valve.

One of the primary failure modes of most valves is damaged sealingsurfaces. One of the reasons for this is the common use of elastomericor rubberized seals in hazardous environments like those encountered inthe production of hydrocarbons such as crude oil or natural gas. The useof elastomers or rubberized components can create increased risks fordegradation and failure within the valve and create increasedmaintenance costs due to the location of the damaged seals or valvecomponents and lead to production down time.

Another problem with existing plug valve designs is that theytraditionally seal only on one side of the valve, generally thedownstream side, when considering the typical direction of the fluidflow through the valve. This design is prone to failure fromcontamination of the sealing surfaces because the sealing surfaces areonly engaged when the valve is closed. When the valve is open, there isa gap between the sealing surfaces. The lack of constant engagementallows chemicals and/or particulates in the fluid stream to degrade thesealing surfaces to the point that they no longer effectuate a seal. Forexample, sand or other particulate matter may cause abrasion of thesealing surface, particularly if the seal is formed from an elastomericmaterial. Separate from the risk of abrasion, particulate matter such assand may remain in the gap between sealing surfaces when an operator isattempting to open or close the valve and may physically interfere withthe formation of a solid seal and/or may increase the difficulty ofrotating the valve to or from an open or closed position.

The gap between sealing surfaces in a typical plug valve is alsoproblematic because valves generally require grease to function; withoutgrease or some other lubricant in the valve body, the plug or ballcannot rotate to a closed position. A gap between sealing surfacestypically allows grease to move from the interior of the valve body tothe fluid stream. This migration of grease creates a loss of lubricationwhich can result in the plug being unable to rotate to the open (orclosed) position.

Although there are other valve designs with double seals, like thatfound in U.S. Pat. No. 5,624,101, those designs generally rely on doubleenergization of the seals in order to create a double sealing mechanismand reliance on a block and bleed function to normalize pressure on theseals. This block and bleed function can lead to similar seal issues asdescribed above.

Another problem with certain prior art plug valves is that when in theclosed position, the plug and the valve body may seize under highpressures. When high working pressures exist in fluid either downstreamor upstream of the plug valve, the plug cannot move from its sealedposition due to the high pressure forces exerted on the valve and getsstuck in place. The likelihood of such an occurrence is higher when thevalve body has lost grease, a problem already discussed above. Thesehigh pressure environments can be hazardous and create issues withmaintenance of the plug valve as well as potential failure mechanismsfor the plug valve itself when operated against such high pressures. Atthe same time, the standard design can also be prone to leaking at lowpressures because the design is meant to be at a high pressure to engagethe sealing surfaces when the valve is closed. The aforementionedproblem with grease loss can also exacerbate the problem with leaking atlow pressure, as grease often serves as the low pressure seal inexisting valve designs.

For the above reasons and others, standard existing valve designs areoften unreliable. The unreliability of these valves frequently promptsusers to stack multiple valves together to ensure they are able to stopthe flow of fluid.

The present invention addresses the unmet need for a valve that can beseated in hazardous environments, high pressure environments, with moreeasily replaceable parts, and/or creates a pressure differential at theseats automatically based on the geometry of the components used toprovide a sealing surface against the plug.

SUMMARY OF THE INVENTION

An aspect of the present invention is to create a valve with a seat andseat bushing configuration such that the seat is maintained in sealingcontact with the plug body regardless of whether the valve is in theopened or closed position.

In an exemplary embodiment, the seat and seat bushing are both locatedin a recess of the valve body and configured such that, when the valveis in the open position, the seat is maintained in sealing engagementwith the flow barrier on both the upstream and downstream sides of thevalve.

The seat is generally annular in shape with two radial surface areas.When the valve is in the open condition, the fluid in the interior boreexerts pressure on both surface areas of the seat but, due to adifferential in the two surface areas, a net positive force tends tourge the seat into sealing engagement with the flow barrier. Inaddition, the fluid also exerts pressure on the radial surface area ofthe seat bushing closest to the flow barrier, tending to push the seatbushing away from the flow barrier. However, the opposite side of theseat bushing, the radial surface farthest from the flow barrier, engageswith a shoulder of the valve body, rather than the seat. Accordingly,the pressure exerted on the seat bushing does not interfere with theseal between the seat and the flow barrier.

When the valve is in the closed position, a primary seal is maintainedon the upstream side similar to when the valve is in the open position,while a secondary seal is also maintained on the downstream side of thevalve.

In an exemplary embodiment, in addition to an improved sealingmechanism, the seat and seat bushing are formed from stainless steel oranother metal, rather than the rubber or elastomeric seals generallyfound in prior art plug valves. This provides for increased durability,longer life between required maintenance, and a more robustmetal-to-metal seal.

In an exemplary embodiment, in addition to an improved sealingmechanism, the seat bushing and seat each comprise corresponding keyedportions that allow for easy removal of the seat for maintenancepurposes during down time or for inspection. Rotating the seat bushingrelative to the seat can engage the keyed portions to allow the seatbushing to assist with the removal of the seat from the valve body, orcan disengage the keyed portions to allow the seat bushing to beseparated from the seat. This provides for reduced maintenance time andreduced cost of maintenance.

References throughout the description to “upstream” and “downstream”should not be interpreted as limiting which term could be used to referto which particular portion of the invention. Those of skill in the artwill understand that which portion of the valve is upstream ordownstream depends on which direction fluid is flowing, and is thereforeunrelated to the structure of the device itself.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific embodiments of the invention are described below with referenceto the figures accompanying this application. The scope of the inventionis not limited to the figures.

FIG. 1 depicts a perspective view of an embodiment of the plug valvewhen it is manufactured with flanges ready to be installed.

FIG. 2 depicts a side view of the interior of the embodiment shown inFIG. 1.

FIG. 3 depicts a close up view of the seat and seat bushing in relationto the plug and valve body when the embodiment of the valve shown inFIG. 1 is in the open position.

FIG. 4 depicts the same view as FIG. 3, with annotations indicating thepressure exerted by fluid when the valve is in the open position.

FIG. 5 depicts the same view as FIG. 4, when the valve is in the closedposition.

FIG. 6 depicts a side view of the interior of an embodiment of the valvebody for an alternative gate valve embodiment.

FIG. 7 depicts a close-up view of the seat and seat bushing in relationto the gate and valve body when the alternative gate valve embodimentshown in FIG. 7 is in the closed position.

FIG. 8 depicts a close-up side view of the alternative gate valveembodiment shown in FIG. 7, with the valve in the open position andannotations indicating the pressure exerted by fluid when thealternative gate valve embodiment is in this position.

FIG. 9 depicts the same view as FIG. 8, when the valve is in the closedposition.

FIGS. 9A-9B depict close-up side views of the seat and seat bushing inrelation to the gate and valve body of additional alternative gate valveembodiments including a biasing member.

FIG. 10 depicts a side view of the interior of the body of analternative embodiment of a gate valve comprising a body bushing.

FIG. 11 depicts a close-up view of the seat, body bushing, and seatbushing in relation to the gate and valve body when the embodiment ofthe valve shown in FIG. 10 is in the open position.

FIG. 12 depicts the same view as FIG. 11, with annotations indicatingthe pressure exerted by fluid when the valve is in the open position.

FIGS. 12A-12B depict close-up side views of the seat, body busing, andseat bushing in relation to the gate and valve body of additionalalternative gate valve embodiments including a biasing member.

FIG. 13 depicts the same view as FIG. 12, when the valve is in theclosed position.

FIG. 14 depicts the keyed portions of the seat bushing and seat of analternative embodiment of the valve.

FIG. 15 depicts the seat bushing being displaced relative to the valvebody to engage the seat bushing's keyed portions with the seat's keyedportions for more easily removing the seat from the body of the valve.

FIG. 15A depicts the seat shown in FIG. 15 being removed from the valvebody using the engagement of the keyed portions of the seat and seatbushing.

FIG. 16 depicts the keyed portions of the seat bushing and seatdisengaged to allow them to be separated from one another.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the valve 100 includes a flanged connection to beinstalled in an oil and gas production area or similar application. Thefluid enters into the valve at the upstream flanged connection 10 and isallowed to flow through the valve body 20 and exits the downstreamflanged connection 30. The valve is operable by a valve stem thatconnects to the plug and is operable to rotate the plug from the open toclosed position. The operation of the valve may be controlled byhydraulic actuator 40. Other types of actuators, including electronic,could also be used.

Referring to FIG. 2, an exemplary embodiment of the valve 100 is shown.Extending between upstream flanged connection 10 and downstream flangedconnection 30 is interior bore 110.

Within valve body 20 is disposed plug 120, seat 130 and seat bushing140. Seat 130 and seat bushing 140 are generally annular in shape andboth located within recess 150 formed in the valve body. Both seat 130and seat bushing 140 may be formed of metal, such as stainless steel.Cavity 106 is formed within valve body 20 and plug 120 rotates withincavity 106. Fluid may flow through interior bore 110 in the directionindicated by arrow F but, as noted above, fluid may also flow in theopposite direction and the valve will still function as described below.

Referring to FIG. 3, the downstream side of seat 130 comprises surface200. Surface 200 is adjacent to valve body 20 at interface 300. Theupstream side of seat 130 comprises surface 210. Surface 210 is adjacentto plug 120 at interface 310. As shown, seat 130 may have a generally“L-shaped” configuration, such that surface 200 is larger than surface210. In addition, there is a radially projecting shoulder 215 formed inthe intermediate portion of seat 130. Thus, the outer surface of seat130 comprises two distinct portions, surface 212 on the upstream sideand surface 214 on the downstream side.

The downstream side of seat bushing 140 comprises surface 220. As shownin FIG. 3, recess 150 has a stepped configuration which forms radiallyprojecting shoulder 230. At interface 320, shoulder 230 contacts aportion of surface 220 on seat bushing 140. The remainder of surface 220on seat bushing 140 does not make contact with any other portion ofvalve 100. Instead, there is a chamber 340 formed by portions of surface220, shoulder 215, surface 212, and shoulder 230. Chamber 340 willgenerally enclose an area of relatively low pressure, compared to theother portions of valve 100. The upstream side of seat bushing 140comprises surface 240. Surface 240 does not contact any other portion ofvalve 100. Seat bushing 140 also comprises bottom surface 250, whichcontacts surface 212. Seat 130 and seat bushing 140 make contact witheach other at the interface formed between surface 250 and surface 212.

In operation, when valve 100 is in the open position, the fluid withinthe interior bore 110 and cavity 106 will generally be at the samepressure. The fluid will generally exert pressure P1 on surface 200 ofseat 130 at interface 300. This pressure will be exerted in an axialdirection, as shown by the arrows in FIG. 4. Pressure P2 will also beexerted in the opposite axial direction on surface 210 of seat 130 atinterface 310. Pressure P3 will also be exerted, in the same axialdirection as P2, on surface 240 of seat bushing 140.

Due to the difference in surface area between surface 200 and surface210, the total force (pressure times surface area) exerted by pressureP1 is greater than the total force exerted by pressure P2. Thisdifferential in force tends to urge seat 130 into sealing engagementwith plug 120 at interface 310. In addition, although pressure P3 isexerted in the opposite direction of P1, it does not interfere with thesealing engagement of seat 130 because the combination of shoulder 230and chamber 340 prevents surface 220 of seat bushing 140 from cominginto contact with seat 130. Instead, pressure P3 is countered by areaction force at shoulder 230. Accordingly, the differential in forceresulting from pressure P1 as compared to P2 is sufficient to ensure arobust metal-to-metal seal at interface 310. In addition, as notedabove, as the pressure within interior bore 110 increases, thedifference in force exerted by P1 and P2 will also increase and so theperformance of the seal, and thus the valve, will improve as theinterior pressure increases. The foregoing description of the operationof valve 100 in the open position applies equally to the upstream anddownstream side of plug 120.

In certain situations, the fluid pressure in cavity 106 may be higherthan the fluid pressure in bore 110. One point at which this scenariomay occur is after pressure has been drained completely from bore 110,and the previous operating pressure, sometimes as high as 15,000 psi,may be contained in cavity 106. Such a pressure differential can bedangerous for personnel working in proximity to the valve, including forexample maintenance personnel who attempt to service the valve whilehigh pressure is trapped in cavity 106. To address such a situation,seat 130 may include a surface 216 at a smaller diameter than surface212 to serve as a pressure-relieving feature for cavity 106. As shown inFIG. 4, surface 212 may take the form of a beveled corner. In thisembodiment, the pressure in cavity 106 will cause a force P5 to beexerted on surface 216 with some component of the force acting in theaxial direction away from plug 120. When the pressure in bore 110 issmall enough such that the force P1 is smaller than the force P5, seat130 will move away from plug 100, which will allow pressure in cavity106 to drain into bore 110 across surface 210.

When valve 100 is in the closed position, the operation of valve body20, plug 120, seat 130, and seat bushing 140 on the upstream side ofplug 120 is essentially the same as that described above. Thus, theoperation on the upstream side is independent of whether the valve is inthe open or closed position.

When valve 100 is in the closed position, a seal is maintained on thedownstream side of plug 120, but potentially via a different mechanism.If pressure is equalized, such that there remains approximately equalpressure on both the upstream and downstream sides of plug 120, then thesealing mechanism will be essentially the same as that described abovewhen valve 100 is in the open position. However, if pressure is notequalized, such that upstream pressure exceeds downstream pressure, asshown in FIG. 5, pressure P4 is exerted by plug 120 in an axialdirection but there is no (or lesser) pressure acting in the oppositedirection of pressure P4. Accordingly, pressure P4 will tend to forceplug 120 into seat 130 at interface 310. In this way, when valve 100 isin the closed position, a seal is maintained on both the upstream anddownstream sides of plug 120, regardless of the relative pressure oneither side of the plug.

As also shown in FIGS. 3 and 4, additional seals may be disposed at theinterfaces between surface 250 of seat bushing 140 and surface 212 ofseat 130, the interface between surface 214 of seat 130 and valve body20, and/or the interface between the top surface of seat bushing 140 andvalve body 20. Such seals may be elastomeric such as, for example,o-rings.

Referring to FIG. 6, an alternative embodiment is shown using a gatevalve 400, rather than a valve that rotates, such as a plug or ballvalve. Although the orientation of the components differs from theembodiment shown in FIGS. 1-5, the basic concept is the same. Extendingbetween upstream flanged connection 410 and downstream flangedconnection 430 is interior bore 510.

Within valve body 420 is disposed gate 520, seat 530 and seat bushing540. Seat 530 and seat bushing 540 are generally annular in shape andboth located within recess 550 formed in the valve body. Cavity 406 isformed within valve body 420 and gate 520 moves within cavity 406.Referring to FIG. 7, the downstream side of seat 530 comprises surface600. Surface 600 is adjacent to valve body 420 at interface 700. Theupstream side of seat 530 comprises surface 610. Surface 610 is adjacentto gate 520 at interface 710. As shown, seat 530 may have a generally“L-shaped” configuration, such that surface 600 is larger than surface610. In addition, there is a radially projecting shoulder 615 formed inthe intermediate portion of seat 530. Thus, the outer surface of seat530 comprises two distinct portions, surface 612 on the upstream sideand surface 614 on the downstream side.

The downstream side of seat bushing 540 comprises surface 620. As shownin FIG. 7, recess 550 has a stepped configuration which forms radiallyprojecting shoulder 630. At interface 720, shoulder 630 contacts aportion of surface 620 on seat bushing 540. The remainder of surface 620on seat bushing 540 does not make contact with any other portion ofvalve 400. Instead, there is a chamber 740 formed by portions of surface620, shoulder 615, surface 612, and shoulder 630. Chamber 740 willgenerally enclose an area of relatively low pressure, compared to theother portions of valve 400. The upstream side of seat bushing 540comprises surface 640. Surface 640 does not contact any other portion ofvalve 400. Seat bushing 540 also comprises bottom surface 650, whichcontacts surface 612. Seat 530 and seat bushing 540 make contact witheach other at the interface formed between surface 650 and surface 612.

In operation, when valve 400 is in the open position, the fluid withinthe interior bore 510 will generally exert pressure P5 on surface 600 ofseat 530 at interface 700. This pressure will be exerted in an axialdirection, as shown by the arrows in FIG. 8. Pressure P6 will also beexerted in the opposite axial direction on surface 610 of seat 530 atinterface 710. Pressure P7 will also be exerted, in the same axialdirection as P6, on surface 640 of seat bushing 540.

Due to the difference in surface area between surface 600 and surface610, the total force (pressure times surface area) exerted by pressureP5 is greater than the total force exerted by pressure P6. Thisdifferential in force tends to urge seat 530 into sealing engagementwith gate 520 at interface 710. In addition, although pressure P7 isexerted in the opposite direction of P5, it does not interfere with thesealing engagement of seat 530 because the combination of shoulder 630and chamber 740 prevents surface 620 of seat bushing 540 from cominginto contact with seat 530. Instead, pressure P7 is countered by areaction force at shoulder 630. Accordingly, the differential in forceresulting from pressure P5 as compared to P6 is sufficient to ensure arobust metal-to-metal seal at interface 710. In addition, as notedabove, as the pressure within interior bore 510 increases, thedifference in force exerted by P5 and P6 will also increase and so theperformance of the seal, and thus the valve, will improve as theinterior pressure increases. The foregoing description of the operationof valve 400 in the open position applies equally to the upstream anddownstream side of gate 520.

When valve 400 is in the closed position, the operation of valve body420, gate 520, seat 530, and seat bushing 540 on the upstream side ofgate 520 is essentially the same as that described above. Thus, theoperation on the upstream side is independent of whether the valve is inthe open or closed position.

It will be understood by those of skill in the art that seat 530 mayinclude a pressure relief feature similar to that described above inconnection with seat 130, such that valve 400 will not experienceextreme pressure differentials between cavity 406 and bore 510.

When valve 400 is in the closed position, a seal is maintained on thedownstream side of gate 520, but potentially via a different mechanism.If pressure is equalized, such that there remains approximately equalpressure on both the upstream and downstream sides of gate 520, then thesealing mechanism will be essentially the same as that described abovewhen valve 400 is in the open position. However, if pressure is notequalized, such that upstream pressure exceeds downstream pressure, asshown in FIG. 9, pressure P8 is exerted by gate 520 in an axialdirection but there is no (or lesser) pressure acting in the oppositedirection of pressure P8. Accordingly, pressure P8 will tend to forcegate 520 into seat 530 at interface 710. In this way, when valve 400 isin the closed position, a seal is maintained on both the upstream anddownstream sides of gate 520, regardless of the relative pressure oneither side of the gate.

Referring to FIG. 9A, an alternative embodiment of valve 400 is shown.Support 760 may be attached to seat 530 and extending in a generallyradial direction, with biasing member 750 extending axially betweensupport 760 and valve body 420. Biasing member 750 may be a spring, aBelleville washer, or any other suitable device that is biased to exertaxial pressure on support 760 in the direction of gate 520. Support 760may be a post, arm, spoke, or any radially extending structureconfigured to transmit the axial force exerted by biasing member 750. Asa result of the attachment between seat 530 and support 760, the axialforce exerted by biasing member 750 assists in maintaining a sealbetween seat 530 and gate 520, particularly under low-pressure operatingconditions. As shown in FIG. 9B, biasing member 750 may instead extendaxially between support 760 and seat bushing 540.

Referring to FIG. 10, an alternative embodiment of a valve 800 is shown.Similar to valve 100 shown in FIG. 2, extending between upstream flangedconnection 810 and downstream flanged connection 830 is interior bore805.

Within valve body 820 is disposed gate 920, seat 930, seat bushing 940,and body bushing 945. Seat 930, seat bushing 940, and body bushing 945are generally annular in shape and both located within recess 950 formedin the valve body. Seat 930, seat bushing 940, and body bushing 945 maybe formed of metal, such as stainless steel. Alternatively, seat 930 maybe formed of a material different from seat bushing 940 and/or bodybushing 945, in order to be more resistant to the forces exerted on seat930 as a result of its sealing engagement with gate 920. Cavity 806 isformed within valve body 820 and gate 920 moves within cavity 806. Fluidmay flow through interior bore 805 in the direction indicated by arrow Fbut, as noted above in connection with the other disclosed embodiments,fluid may also flow in the opposite direction and the valve will stillfunction as described below.

Referring to FIG. 11, the downstream side of body bushing 945 comprisessurface 1000. Surface 1000 is adjacent to valve body 820 at interface1100. The upstream side of body bushing 945 comprises surface 1120. Thedownstream side of seat 930 comprises surface 1130. Surface 1120 of bodybushing 945 is adjacent to surface 1130 of seat 930 at interface 1140.As shown in FIG. 11, the area of surface 1120 and the area of surface1130 are preferably substantially equivalent.

The upstream side of seat 930 comprises surface 1010. Surface 1010 isadjacent to gate 920 at interface 1110. As shown, seat 930 may have agenerally “L-shaped” configuration, such that surface 1010 is smallerthan surface 1130. Similarly, surface 1000 of body bushing 945 may besmaller than surface 1120. In addition, there is a radially projectingshoulder 1015 formed in the intermediate portion of seat 930. Thus, theouter surface of seat 930 comprises two distinct portions, surface 1012on the upstream side and surface 1014 on the downstream side.

The downstream side of seat bushing 940 comprises surface 1020. As shownin FIG. 11, body bushing 945 has a stepped configuration which formsradially projecting shoulder 1030. At interface 1025, shoulder 1030 ofbody bushing 945 contacts a portion of surface 1020 on seat bushing 940.The remainder of surface 1020 on seat bushing 940 does not make contactwith any other portion of valve 800. Instead, there is a chamber 1170formed by portions of surface 1020, shoulder 1015, surface 1012, andshoulder 1030. Chamber 1170 will generally enclose an area of relativelylow pressure, compared to the other portions of valve 800. The upstreamside of seat bushing 940 comprises surface 1040. Surface 1040 does notcontact any other portion of valve 800. Seat bushing 940 also comprisesbottom surface 1050, which contacts surface 1012. Seat 930 and seatbushing 940 make contact with each other at the interface formed betweensurface 1050 and surface 1012.

In operation, when valve 800 is in the open position, the fluid withinthe interior bore 805 and cavity 806 will generally be the samepressure. The fluid will generally exert pressure P10 on surface 1130 ofseat 930 at interface 1140. This pressure will be exerted in an axialdirection, as shown by the arrows in FIG. 12.

Pressure P11 will also be exerted in the opposite axial direction onsurface 1010 of seat 930 at interface 1110. Pressure P12 will also beexerted, in the same axial direction as P11, on surface 1040 of seatbushing 940.

Due to the difference in surface area between surface 1130 and surface1010, the total force (pressure times surface area) exerted by pressureP10 is greater than the total force exerted by pressure P11. Thisdifferential in force tends to urge seat 930 into sealing engagementwith gate 920 at interface 1110. In addition, although pressure P12 isexerted in the opposite direction of P10, it does not interfere with thesealing engagement of seat 930 because the combination of shoulder 1030of body bushing 945 and chamber 1170 prevents surface 1020 of seatbushing 940 from coming into contact with seat 930. Instead, pressureP12 transfers to body bushing 945 by a reaction force P13 at shoulder1030, causing body bushing 945 to axially engage valve body 820 atinterface 1100. Accordingly, the differential in force resulting frompressure P10 as compared to P11 is sufficient to ensure a robustmetal-to-metal seal at interface 1110. In addition, as noted above, asthe pressure within interior bore 805 increases, the difference in forceexerted by P10 and P11 will also increase and so the performance of theseal, and thus the valve, will improve as the interior pressureincreases.

It will be understood by those of skill in the art that seat 930 mayinclude a pressure relief feature similar to that described above inconnection with seat 130, such that valve 800 will not experienceextreme pressure differentials between cavity 806 and bore 805.

The foregoing description of the operation of valve 800 in the openposition applies equally to the upstream and downstream side of gate920. When valve 800 is in the closed position, the operation of valvebody 820, gate 920, seat 930, seat bushing 940 and body bushing 945 onthe upstream side of gate 920 is essentially the same as that describedabove. Thus, the operation on the upstream side is independent ofwhether the valve is in the open or closed position.

When valve 800 is in the closed position, a seal is maintained on thedownstream side of gate 920, but potentially via a different mechanism.If pressure is equalized, such that there remains approximately equalpressure on both the upstream and downstream sides of gate 920, then thesealing mechanism will be essentially the same as that described abovewhen valve 800 is in the open position. However, if pressure is notequalized, such that upstream pressure exceeds downstream pressure, asshown in FIG. 13, pressure P14 is exerted by gate 920 in an axialdirection but there is no (or lesser) pressure acting in the oppositedirection of pressure P14. Accordingly, pressure P14 will tend to forcegate 920 into seat 930 at interface 1110. Seat 930 will exert pressureP15 on seat bushing 945 by virtue of the contact between surface 1120 ofbody bushing 945 and surface 1130 of seat 930 at interface 1140. In thisway, when valve 800 is in the closed position, a seal is maintained onboth the upstream and downstream sides of gate 920, regardless of therelative pressure on either side of the plug.

As also shown in FIGS. 10-13, additional seals may be disposed at thevarious interfaces between the surfaces of seat 930, seat bushing 940,and body bushing 945. Although these seals may be elastomeric, similarto those described above in connection with the other embodiments, theembodiment shown in FIGS. 10-13 provides at least one additionaladvantage. Because seat 930 does not directly contact valve body 820,there is no need for any of the seals to be located in a recess formedby removing material from either seat 930 or valve body 820. As shown inFIGS. 10-13, all seals may be located in grooves formed in seat bushing940 or body bushing 945, which aids in manufacturing and durability ofthe overall design of valve 800.

As also shown in FIGS. 10-13, biasing member 1150 may be located betweenannular shoulder 1160 of body bushing 945 and valve body 820. Biasingmember 1150 may be a spring, a Belleville washer, or any other suitabledevice that is biased to exert axial pressure on annular shoulder 1160in the direction of gate 920. As a result of the contact between surface1120 of body bushing 945 and surface 1130 of seat 930 at interface 1140,the axial force exerted by biasing member 1150 assists in maintaining aseal between seat 930 and gate 920, particularly under low-pressureoperating conditions.

As also shown in FIGS. 10-13, seat bushing 940 and body bushing 945 maybe connected through the use of attachment member 1180. Attachmentmember 1180 may be a screw, pin, or any other suitable device to fixedlyconnect seat bushing 940 and body bushing 945, ensuring that surface1040 of seat bushing 940 does not contact gate 920.

The addition of body bushing 945 has several potential benefits incomparison to the embodiment shown in FIGS. 1-9. The use of body bushing945 allows for the use of a seat 930 that is significantly smaller thanseat 130. The seat is generally the component within this type of valvethat must be replaced the most frequently, and it is often formed ofmaterials that are more expensive than those used to form the othercomponents. Accordingly, using a smaller seat makes the overall designof the valve more economical. In addition, as noted above, the use ofbody bushing 945 avoids potential problems associated with locatingsealing elements within grooves formed in either seat 930 or valve body820. In addition, the use of body bushing 945 facilitates the use ofbiasing member 1150 to aid in low-pressure sealing.

Referring to FIG. 12A, an alternative embodiment of valve 800 is shown.Support 1170 may be attached to seat 930 and extending in a generallyradial direction, with biasing member 1150 extending axially betweensupport 1170 and body bushing 945. Biasing member 1150 may be a spring,a Belleville washer, or any other suitable device that is biased toexert axial pressure on support 1170 in the direction of gate 920.Support 1170 may be a post, arm, spoke, or any radially extendingstructure configured to transmit the axial force exerted by biasingmember 1150. As a result of the attachment between seat 930 and support1170, the axial force exerted by biasing member 1150 assists inmaintaining a seal between seat 930 and gate 920, particularly underlow-pressure operating conditions. As shown in FIG. 12B, biasing member1150 may instead extend axially between support 1170 and seat bushing940.

Referring to FIG. 14, an alternative embodiment of a valve 400 is shown.This embodiment shows the potential for use of a keyed seat bushing 940and seat 931 relative to valve body 420 to facilitate removal of seat931 from valve body 420. Seat 931 may have a keyed portion at 1141 andseat bushing 940 may have a keyed portion at 1140. FIG. 14 shows thekeyed portions when seat bushing 940 and seat 931 are installed in valvebody 420 during standard operation of valve 400. FIG. 15 shows seatbushing 940 partially removed from valve body 420 such that keyedportion 1140 of seat bushing 940 is engaged with keyed portion 1141 ofseat 931 during disassembly of valve 400. FIG. 15A shows seat bushing940 removing seat 931 from valve body 420 via keyed portions 1140 and1141. FIG. 16 shows the disengaged arrangement of keyed portions 1140and 1141 to allow seat bushing 940 and seat 931 to be separated fromeach other when one of them is rotated. Thus, the operation of the valvewould not be diminished through the use of the keyed seat 931 and seatbushing 940, but rather maintenance cost and down time would be reducedbecause of the ability to more quickly change out a worn seat 931 in thevalve 400. It is understood that variations may be made in the foregoingwithout departing from the scope of the present disclosure. In severalexemplary embodiments, the elements and teachings of the variousillustrative exemplary embodiments may be combined in whole or in partin some or all of the illustrative exemplary embodiments. In addition,one or more of the elements and teachings of the various illustrativeexemplary embodiments may be omitted, at least in part, and/or combined,at least in part, with one or more of the other elements and teachingsof the various illustrative embodiments.

Any spatial references, such as, for example, “upper,” “lower,” “above,”“below,” “between,” “bottom,” “vertical,” “horizontal,” “angular,”“upwards,” “downwards,” “side-to-side,” “left-to-right,”“right-to-left,” “top-to-bottom,” “bottom-to-top,” “top,” “bottom,”“bottom-up,” “top-down,” etc., are for the purpose of illustration onlyand do not limit the specific orientation or location of the structuredescribed above.

In several exemplary embodiments, while different steps, processes, andprocedures are described as appearing as distinct acts, one or more ofthe steps, one or more of the processes, and/or one or more of theprocedures may also be performed in different orders, simultaneouslyand/or sequentially. In several exemplary embodiments, the steps,processes, and/or procedures may be merged into one or more steps,processes and/or procedures.

In several exemplary embodiments, one or more of the operational stepsin each embodiment may be omitted. Moreover, in some instances, somefeatures of the present disclosure may be employed without acorresponding use of the other features. Moreover, one or more of theabove-described embodiments and/or variations may be combined in wholeor in part with any one or more of the other above-described embodimentsand/or variations.

Although several exemplary embodiments have been described in detailabove, the embodiments described are exemplary only and are notlimiting, and those skilled in the art will readily appreciate that manyother modifications, changes and/or substitutions are possible in theexemplary embodiments without materially departing from the novelteachings and advantages of the present disclosure. Accordingly, allsuch modifications, changes, and/or substitutions are intended to beincluded within the scope of this disclosure as defined in the followingclaims. In the claims, any means-plus-function clauses are intended tocover the structures described herein as performing the recited functionand not only structural equivalents, but also equivalent structures.Moreover, it is the express intention of the applicant not to invoke 35U.S.C. § 112, paragraph 6 for any limitations of any of the claimsherein, except for those in which the claim expressly uses the word“means” together with an associated function.

What is claimed is:
 1. A valve comprising: a valve body comprising acavity and an interior bore with a central longitudinal axis; a flowbarrier disposed within said cavity and operable to move between an openposition in which the interior bore of the valve body is unobstructedand a closed position in which the flow barrier obstructs the interiorbore; a generally annular recess formed in the valve body; a seatdisposed within said recess, said seat comprising a first radial surfaceadjacent to said flow barrier and a second radial surface, the secondradial surface being larger than the first radial surface; a seatbushing disposed within said recess, said seat bushing comprising afirst radial surface; said seat bushing and seat disposed such that thefirst radial surface of the seat bushing does not directly contact theseat.
 2. The valve of claim 1 further comprising a body bushingcomprising a first radial surface, a second radial surface, and a thirdradial surface, configured such that: the first radial surface isadjacent to the valve body; the second radial surface is adjacent to thesecond radial surface of the seat; and the third radial surface isadjacent to the first radial surface of the seat bushing.
 3. The valveof claim 2 in which the area of the first radial surface of the bodybushing is substantially equal to the second radial surface of the seat.4. The valve of claim 2 in which the body bushing further comprises afourth radial surface and the valve further comprises a biasing memberdisposed between said fourth radial surface and the valve body.
 5. Thevalve of claim 2 further comprising a biasing member disposed betweenthe valve body and the first radial surface of the body bushing.
 6. Thevalve of claim 1 in which the seat further comprises a first keyedportion and the seat bushing further comprises a second keyed portionconfigured to engage with the first keyed portion, such that the seatbushing may be used to remove the seat.
 7. The valve of claim 2, furthercomprising one or more elastomeric sealing elements disposed within agroove formed in an outer surface of the body bushing.
 8. The valve ofclaim 1, in which the seat bushing comprises a second radial surfacewhich does not contact any other portion of the valve.
 9. The valve ofclaim 2, in which the seat bushing is fixedly connected to the bodybushing.
 10. The valve of claim 1 in which the flow barrier comprises aplug.
 11. The valve of claim 1 in which the flow barrier comprises aball.
 12. The valve of claim 1 in which the flow barrier comprises agate.
 13. The valve of claim 1 in which the seat is comprised of metal,such that contact between the first radial surface and the flow barriercreates a metal-to-metal seal.
 14. The valve of claim 1 in which theseat further comprises a support and a biasing member is disposedbetween the support and the valve body.
 15. The valve of claim 1 inwhich the seat further comprises a support and a biasing member isdisposed between the support and the seat bushing.
 16. The valve ofclaim 2 in which the seat further comprises a support and a biasingmember is disposed between the support and the body bushing.
 17. Thevalve of claim 2 in which the area of the first radial surface of thebody bushing is smaller than the area of the second radial surface ofthe body bushing.
 18. The valve of claim 1 in which: the seat bushingfurther comprises a first axial surface; and the seat further comprises:a second axial surface adjacent to the first axial surface of the seatbushing; and a third surface that intersects both the first radialsurface and the second axial surface.